The disclosure relates to a method for moving an industrial machine for maintenance such as a generator from an aligned single shaft gas turbine-generator-steam turbine configuration.
Large industrial machines such as a gas turbine, generator and steam turbine are often aligned with other structures for operation. For example, the gas turbine, generator and steam turbine may be axially aligned in a single shaft configuration one with the other with the generator located between the gas and steam turbines whereby the turbines drive the generator rotor to produce electric power. This configuration is known as a single shaft STAG (steam and gas) combined-cycle system. In the single shaft STAG combined-cycle system, it will be appreciated that the opposite ends of the generator are mechanically coupled to the gas and steam turbines, respectively. The generators of these systems, similar to other industrial machines, are generally mounted on foundations prepared for supporting these large system generators. Typically, large industrial machines or parts thereof such as the generator rotor, i.e., the generator field, must be removed from the machines for scheduled maintenance or repair. In terms of the generator example, with the three main rotating components of the single shaft combined-cycle system secured to the foundation, and in axial alignment one with the other parts, it is not possible to remove the generator field axially due to the lack of clearance with respect to the turbines at opposite ends of the generator. Maintenance on the gas and steam turbines can typically be performed in situ because the turbine housings are split along a horizontal midline enabling removal of each upper casing, exposing the rotors of the gas and steam turbines. This leaves the lower turbine casings resting on the foundation. However, because the generator is an electromagnetic generator, it is not typically possible to split the generator rotor and casing at the centerline and lift the generator rotor from the generator in a vertical direction. Similar clearance limitations plague maintenance of other industrial machines.
With regard to generators, prior maintenance has been performed on rotors in single shaft combined-cycle systems, primarily in three ways. Once the generators are mechanically uncoupled from the turbines, the generators are directly lifted (via gantry or crane) from the foundation and moved to a laydown area in the plant where rotor removal in an axial direction is not hindered by the presence of other equipment. Often it is necessary to bring in specialized heavy-duty lifting equipment for these lifts as on-site lift capability is usually inadequate to perform such lifts. Another prior process for maintaining generator rotors requires a movable slab forming part of the foundation for the generator. With the generator located on the movable slab, the generator may be displaced transversely or laterally from between the turbines and thus moved to a position where the turbines do not interfere with axial removal of the generator field. Another prior process mounts the generator on special foundations having removable portions that allow installation of guides that allow rotation of the generator about a vertical axis, thus allowing removal of the generator field. Similar complex configurations are used widely for other forms of large industrial machines.